This invention relates generally to the field of pressure relief valves and more specifically to a reset relief valve.
Pressure relief valves are important components in certain fluid flow systems in which undesirable high pressure may occur. In such systems, overpressure can damage valuable processing equipment or cause breakdown or rupture of weak components of the system. It is desirable that when a pre-determined or pre-designated threshold pressure is exceeded, the pressure relief valve open very quickly, i.e., virtually instantaneously, to relieve system pressure. Pressure relief valves having this capability are commonly referred to as “pop-off” valves because of their rapid opening action. In carrying out the rapid opening of the valve, movable port-blocking elements within the valve, such as a plug or piston, are subjected to high acceleration and velocity, resulting in severe impact forces being imposed on the piston and other elements of the valve when the moving member reached its limit of travel away from the port-blocking position.
In prior art, the working fluid has been used to lessen impact within a valve by routing the fluid through ports or apertures in a manner to reduce impact forces. For example, U.S. Pat. No. 5,715,861 to Williams shows a fluid flow path whereby the subject fluid flows above the piston to equalize pressure. Fluid hydraulics using the pumped or working fluid have not proven to be effective in that high impact forces often tear internal parts upon initial activation of the valve. In other solutions, cushion members formed of rubber and similar resilient elastomeric materials have been used to attenuate the impact of the flow control piston subsequent to its rapid displacement from the flow-blocking position. Examples of such valves and rubber cushion members are disclosed in U.S. Pat. Nos. 2,973,776 and 2,973,777 respectively issued on Mar. 7, 1961 to Herbert Allen and John N. Troxell, Jr. While the annular elastomeric cushion rings do provide effective initial shock attenuation, the rings, aided by the initial drop in pressure at the inlet port when the piston is moved from its blocking position, promote undesirable rebounding of the piston, which inhibits the free flow of fluid to the outlet port, and impose additional repetitive shock forces on the entire valve assembly. Furthermore, the rebounding action attributed to the resilient rings often resulted in the relief valve resetting itself before release of the excess pressure, only to be triggered soon thereafter by the unrelieved pressure. This opening and unintended resetting cycle could continue for a significant period of time until it was detected, and was a major contributor to wear and failure of the internal linkage mechanism and other components of the valve.
The various solutions in the prior art fail to provide a relief valve that can be manually reset after activation and that withstands the pressures commonly found in their application thereby avoiding damaging impacts on the valve and the need to replace the valve after it is activated.